The present invention relates to the bottom frame of a vehicle particularly a motor vehicle. As is well known in the art, the frame is the basic structure of most motor vehicles andhas mounted upon it or attached to it the power plant, the power train and the body or other seat for the driver and occupants. The frame itself is normally supported by the suspension and must be sufficiently strong and rigid so as to enable it to withstand the various forces to which it is subjected in normal operation.
More particularly, the present invention relates to a motor vehicle frame which is made up of two side members which extend in the longitudinal direction of the vehicle and are located between a respective front wheel and rear wheel of the vehicle, two longitudinal members which are arranged in at least one end region of the vehicle and which, throughout their lengths, are laterally displaced with respect to the side members in the direction toward the longitudinal axis of the vehicle, and two cross members which extend in opposite directions from the generally centrally arranged, longitudinally extending propeller shaft tunnel, these cross members having projecting portions extending into the mentioned end region of the vehicle, which projecting portions serve as a support for the corresponding longitudinal member.
German Patent Application (Auslegeschrift) No. 1,430,738, published Mar. 11, 1971, shows a construction of this type in which those ends of the longitudinal members which are directed toward the side members are downwardly offset and, in the region of the bottom plate, extend parallel to the side members. The cross members have a relatively small cross section and extend, in longitudinal cross section through the vehicle, through only a small upper region of the longitudinal members. Because of this difference in elevation between the cross members and the side members, an additional hollow girder has to be provided on each side of the vehicle, each extending vertically between the outer end of each cross member and the corresponding side member.
The above-described construction has a number of significant drawbacks. For one thing, whenever a load supporting member is displaced in a direction transverse to the longitudinal direction of the vehicle, and this includes the vertical displacement of the cross members with respect to the side members, additional carrier members are needed which are suitably configured and supported so as to enable them to take up bending moments. Moreover, when the longitudinal members extend to the other side of the cross-sectional plane of the cross members, this takes up space in the region of the bottom plate. If, as a result, the longitudinal members are located below the bottom plate, the ground clearance of the vehicle is reduced, whereas if the longitudinal members are placed above the bottom plate, they extend into the passenger compartment. If the vehicle end region in question is the front end, the relatively high position of the cross members makes it difficult to accommodate the steering components.